Effect of Increasing Spray Solution Salinity on Postemergence Herbicide Weed Control and Crop Tolerance

A greenhouse experiment was conducted to establish postemergence  herbicide weed control and crop tolerance to herbicides sprayed with increasing rates of salinity.  The greenhouse is at the Plant Science Research and Education Unit, Citra, FL.  The treatment design was a 4 herbicide x 6 salinity levels x 5 species.  Treatments were arranged in a randomized complete block design with 3 replications.  Herbicides were halosulfuron at 16 g ha^-1, metribuzin at 228 g ha^-1, sethoxydim at 128 g ha^-1, and nontreated.  Salinity levels were established as electrical conductivity (EC) at 0, 1, 2, 3, 4, and 5 ds m^-1.  The five species were green bean, sweet corn, tomato, large crabgrass, and goosegrass.  At 4 weeks after planting, treatments were applied over the top of the plants with a backpack sprayer calibrated to 28 L ha^-1.  Visual ratings for crop injury (0%=no injury, 100%=complete plant death) were collected weekly for 3 weeks after treatment (WAT).  At 6 WAT, plants were harvested at the soil surface and fresh and dry weights were measured.  Data were analyzed using a general linear model and means were separated with Fisher’s Protected LSD.  Herbicide*salinity were not significant and means were combined.  Plant injury at 21 DAT was not significantly different for plant species at all salinity levels.  No anatagonistic or synergistic response between herbicide and salinity for fresh or dry weight.  Salinity did not have an impact on the herbicide efficacy or crop tolerance.  These treatments were applied as a single application and repeat or split applications of herbicides should be investigated further.